This invention relates to gear boxes and, particularly, to gear box structures which are coated with corrosion resistant material for permitting use of the gear box within a corrosive environment, particularly a salt water environment.
Conventional gear boxes are generally devised as a heavy duty tool, particularly constructed to withstand long-time usage under extreme power requirements and under adverse conditions. However, it has been found that the life span for a gear box in a salt water or other harsh environment is reduced considerably from many years to only a few weeks before corrosion deteriorates the gear box beyond further useful service. The materials utilized in conventional gear boxes are generally cast iron and/or steel and, in special applications, stainless steel in order to ensure long life usage. Since cast iron and steel offer little or no protection, eventually stainless was introduced to obviate this problem. However, even stainless steel is not able to survive a salt water environment, and at best, may only prolong the life of the gear box very slightly.
Therefore, it is a principal object of the present invention to enhance the life span of gear boxes under adverse corrosive environments such as those involving salt water, fertilizers, concrete, sewage disposal, and chemical processes.
Another object of the present invention is to improve the art of gear boxes by permitting the use of standard materials susceptible to corrosion in the construction of the same and yet extend the life span for these devices.
These and other objects of the present invention are achieved by the present invention which is directed to a gear box or the like which has a corrosion resistant material coating thereon, preferably a fluorocarbon polymer which is impervious to oxidation, chemical attack and the like. In a most preferred arrangement, two different coatings of fluorocarbon polymers may be applied in particular thickness ranges. The coating thicknesses are devised in accordance with acceptable tolerances associated with each of the details of the gear box assembly in order to avoid any binding in the movement of the parts and the prevention of inadvertent wear of the material from the parts while also affording the desired protection in harsh environments.
In a most preferred embodiment, the outer housing of the gear box or the like is coated with a polymeric material which not only will resist corrosion and chemical attack, but which also has adequate resilience and/or toughness to withstand blows from hammers, wrenches and other foreign objects and which will not chip off the structure. Polyamides such as nylon are most preferred for coating of the outer housing though epoxies and fluorocarbons may also be applied thereto. Other elements which are normally received within the exterior housing and/or otherwise located where damage from foreign objects is not likely are preferably covered with fluorocarbon coatings. Practically speaking, the polytetrafluoroethylenes are most often employed and, when in direct contact with the metal, include a thermoset binder component such as a phenolic for proper adherence to the prepared metal surface. Further, a top coating of polytetrafluoroethylene polymer composition may then be applied atop the base coating for crosslinking therewith.